1. Field of the Invention
The present invention relates to a pump used in an air-conditioner for circulating a liquid refrigerant through a refrigerating system of the air-conditioner.
2. Description of the Prior Art
In the refrigeration and air-conditioning industry, there has recently been proposed an air-conditioner equipped with a pump for circulating a liquid refrigerant through a refrigeration system of the air-conditioner.
The refrigerant circulation pump of the proposed air-conditioner is designated by 1 such as shown here in FIGS. 4 through 7. The pump 1 includes a closed container 2 which is composed of a tubular central shell body 3, a first end shell 5 closing one end 3a of the shell body 3 and provided with an electrode assembly 4 of the so-called "hermetic terminal" type, and a second end shell 8 closing an opposite end of the shell body 3 and provided with a discharge pipe 6 (FIG. 7) and an intake pipe 7. The closed container 2 houses therein an electric motor unit 11 composed of a stator 9 and a rotor 10, a shaft 13 rotatably driven by the rotor 10 and having an eccentric portion 12, a cylinder 16 having defined therein a compression chamber 14 and an intake hole 15 and a discharge hole 19 that communicate with the compression chamber 14, and a roller 17 firmly fitted over the eccentric portion 12 for co-rotation therewith and slidably movable along an inside surface of the compression chamber 14 as the eccentric portion 12 of the shaft 13 rotates within the compression chamber 14. Numeral 18 (FIG. 5) is a vane reciprocally movable in a radial direction within a vane groove 20 extending between the intake hole 15 and the discharge hole 19. The vane 18 is normally urged against the roller 17 by a spring 21. A bearing 22 is disposed adjacent to the cylinder 16 and rotatably supports an intermediate portion 13a of the shaft 13. The bearing 22 has an outer peripheral surface 22a firmly fitted with an inside surface of the closed container 2. The intake pipe 7 communicates with the inside of the closed container 2 and has an end 7a welded as at 23 to the second end shell 8. The discharge pipe 6 extends through the second end shell 8 and has an end 6a press-fitted in the discharge hole 19 in the cylinder 16. A liquid refrigerant 24 is filled in the closed container 2. The interior of the closed container 2 is communicated with the discharge pipe 6 through a pressure equalizing hole 25 (FIG. 7) formed in the discharge pipe 6.
With the foregoing construction, when the motor unit 11 is energized via the electrode assembly 4 to rotate the shaft 3 and the rotor 10, a liquid refrigerant returning from an air-conditioning system (not shown) is introduce through the intake pipe 7 into the interior of the closed container 2 where the refrigerant is stirred and then drawn from the intake hole 15 into the compression chamber 14 in the cylinder 16. As the roller 17 rolls on and along the inside surface of the compression chamber 14, the refrigerant is gradually compressed within the compression chamber 14 and then discharged from the compression chamber 14 through the discharge hole 19. Thereafter, the compressed refrigerant is delivered to an air-conditioning system (not shown) via the discharge pipe 6. As the compressed refrigerant flows through the discharge pipe 6, a very small quantity of liquid refrigerant leaks out from the pressure equalizing hole 26 into the enclosed container 2 so as to keep the interior of the enclosed container 2 at a high pressure.
According to the known refrigerant circulation pump of the foregoing construction, the liquid refrigerant lubricates the shaft 13 and the bearing 22. However, as the level of the liquid refrigerant becomes low, lubrication of the shaft 13 and the bearing 22 is performed insufficiently with the result that the shaft 13 and the bearing 22 wear out severely. The service life of the known refrigerant circulation pump is, therefore, relatively short.